The present invention relates to measurement of the signal-to-noise ratio of communications signals. More specifically, but without limitation thereto, the present invention relates to a device for finding the signal-to-noise ratio of a constant envelope amplitude communications signal having a known modulation scheme.
Current techniques for measuring signal-to-noise ratio require extracting information from the signal, such as bit error rate devices. Examples of such devices may be found, for example, in U.S. Pat. No. 5.440,582 issued on Aug. 8, 1995 to Birchler et al. This device estimates signal quality from a stream of demodulated information extracted from the received signal. U.S. Pat. No. 4,835,790 issued on May 30, 1989 to Yoshida et al. discloses a specially clocked analog-to-digital converter to estimate the quality of a phase-shift keyed signal. U.S. Pat. No. 3,350,643 discloses a device that processes a stream of demodulated data from a digitally encoded transmission to estimate signal quality.
A continued need exists for a device that can find signal-to-noise ratio of a communications signal without the difficulty of having to first extract the transmitted information from the received signal.